As a rotating electric machine operates, the wire of a coil generates heat to raise the temperature. It is known that a failure to sufficiently cool the wire reduces the output of the rotating electric machine and degrades the durability of the wire.
A rectangular wire is in some cases used for a stator winding of such a rotating electric machine to form an edgewise coil. With such a rectangular wire, the coil has a larger cross-sectional area than with a usual round wire, resulting in a reduced direct-current resistance, improved frequency characteristics, and the like. Accordingly, the coil can be reduced in size and improved in performance.
However, the rectangular wire shows a great radius of curvature when making turns, where the wire is likely to leave large gaps from a tooth of a stator (iron core) of the rotating electric machine. Specifically, when winding the rectangular wire around a wind region having a rectangular cross section of an insulating member which covers the iron core, it is difficult to wind the wire in an exact rectangular shape. The wire is inevitably lifted up from the sides of the rectangle while being in contact with the corners, resulting in gaps between the wire and the sides of the rectangle. The gaps, acting as a heat insulating space, raise the problem in that heat generated by the wire is less likely to be transmitted to the iron core through the insulating material, resulting in degraded cooling performance of the wire even if the iron core is cooled.
In light of such a drawback, Japanese Patent Laying-Open No. 2004-343877 (Patent Document 1) discloses coils of a rotating electric machine whose wires can be cooled efficiently with a simple structure. Each coil of the rotating electric machine has a wire wound in multiple layers around a wind region of an insulating member which covers the iron core, and is characterized in that gaps between the wind region of the insulating member and the wire are filled with a thermal conductive material supplied through a channel formed in the insulating member.
With the coils of the rotating electric machine in which the gaps provided between the wind region of the insulating member which covers the iron core and the wire wound around the wind region are filled with a thermal conductive material supplied through the channel formed in the insulating member, transmission of heat of the wire to the iron core through the thermal conductive member and the insulating member allows effective dissipation of the heat to cool the wire. Further, there is no need to provide a coolant, a pump for circulation thereof or the like, which contributes to reduced costs.